Palestinian survivors of a massacre in Lebanon nearly 20 years ago asked a Belgian court yesterday to indict the Israeli Prime Minister, Ariel Sharon, for crimes against humanity over his role in the carnage.

Taking advantage of Belgium's unusually broad laws on war crimes, 28 of those who survived the killings at the Sabra and Chatila refugee camps outside Beirut filed a legal complaint with an investigating judge in Brussels. He will probably take one month to decide whether Mr Sharon and others should face charges for involvement in the murders.

In 1982 up to 2,000 unarmed Palestinians in the camps were slaughtered by a Lebanese Christian militia allied to the Israelis. An Israeli inquiry found Mr Sharon, who was then Defence Minister, "indirectly responsible" and he resigned.

Even if the case goes ahead, Mr Sharon would almost certainly not be arrested if he went to Belgium. But the attempt to purse a war crimes case has already caused a diplomatic incident, and the Israeli Foreign Minister, Shimon Peres, has told the Belgian government that none of his fellow ministers will risk visiting Brussels if the action proceeds.

That creates a headache for Belgium, which takes over the European Union's presidency at the end of the month and will be expected to play a leading role in Europe's efforts to help broker peace in the Middle East.

One of the survivors, Souad Srour Al-Marai, gave harrowing details of the massacre, which took the lives of most of her family. She said: "My little sister, aged 18 months, raised her hand and asked her mother to pick her up, she was frightened. Then they started shooting at us.

"My little sister received a bullet in the head, my father was hit in his chest but was still alive. My brothers and sisters, Chadi [3], Farid [8], Bassam [11], Hajar [7], Chadia [18 months] [and] also our neighbour were all killed by the first bullets."

The woman then said she was raped in front of her dying father and left for dead.

The basis for the case lies in a law dating from 1993 that gives Belgian courts jurisdiction over violations of the Geneva war crimes convention no matter where they happened, even if they involve no Belgian nationals. Earlier this month the legislation was used to convict two nuns who played a role in the genocide in Rwanda in 1994, fuelling a debate over the whole process of war crimes prosecutions.

The Belgian government, concerned at the prospect of dozens of new cases from around the world, and fearful of the political implications, now wants to amend the law.

Vincent Van Quickenborne, a Belgian senator who is sponsoring the case, said that "for Belgium as a state these facts cannot be acceptable. We as a state should indict people and try them to find out whether they have committed these acts."

Michael Verhaeghe, the lawyer who is representing the survivors, said there was "sufficient evidence" to convict those responsible, adding that "the facts in this case undeniably reveal crimes against humanity".

Yesterday's legal action is the second against Mr Sharon to be lodged in Belgium, but it is thought to stand a greater chance of leading to a trial.

The 1982 massacre unfolded over three days when Israel allowed its Lebanese Christian Phalangist militia allies into the refugee camps. Mr Sharon had earlier claimed that there were 2,000 "terrorists" in the camps; Israel later claimed the Phalange were sent into Sabra and Chatila to "mop up" the armed guerrillas supposedly still there after the Palestine Liberation Organisation's withdrawal from Beirut the previous month.

The subsequent Israeli Kahan commission report stated that Israeli troops surrounding the camps knew what was happening. Throughout the killings many of the victims were stabbed and a large number of women were murdered after being gang-raped. Mr Sharon was in overall command of the Israeli forces.

More than 400 of the dead were buried in a mass grave just inside the entrance to the camps. Hundreds of others were buried secretly during the massacre, many of them beneath Beirut golf course.

* Yesterday, we stated that an Israeli inquiry into the 1982 massacre of Palestinan civilians in Lebanon held Ariel Sharon responsible. We have been asked to point out that the inquiry found Mr Sharon to be "indirectly" responsible.